Compressors in refrigeration systems raise the pressure of a refrigerant from an evaporator pressure to a condenser pressure. The evaporator pressure is sometimes referred to as the suction pressure and the condenser pressure is sometimes referred to as the discharge pressure. At the discharge pressure, the refrigerant is capable of cooling a desired medium. Many types of compressors, including rotary screw compressors, are used in such refrigeration systems.
A screw compressor includes a suction port and a discharge port that open into a working chamber of the screw compressor. The working chamber includes a pair of meshed screw rotors that define a compression pocket between the screw rotors and interior walls of the working chamber. Refrigerant is received by the suction port and delivered to the compression pocket. Rotation of the rotors closes the compression pocket from the suction port and decreases the volume of the compression pocket as the rotors move the refrigerant toward the discharge port. Due to decreasing the volume of the compression pocket, the rotors deliver the refrigerant to the discharge port at an discharge pressure that is greater than the suction pressure.